Radio Frequency Identification (RFID) is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency spectrum to identify objects to which RFID tags are affixed. RFID systems in general provide the advantage of not requiring direct contact or line-of-sight scanning. A typical RFID system includes a plurality of RFID readers and a plurality of RFID tags that are affixed to the objects of interest. Each RFID reader includes an antenna and also includes or is coupled to a transceiver. An RFID reader uses the antenna and transceiver to transmit radio frequency signals to the RFID tag. The RFID reader has the ability to select one or more tags by transmitting an identifier that specifies one or more of the tags from a plurality of tags. When an RFID reader selects an RFID tag, the RFID tag is put into a responsive mode, with other tags going into a muted state.
When put into responsive mode, the tag transmits data back to the reader by modulating a backscattered signal that is received at the RFID reader antenna. As one example, some tags use variable impedance coupled to the antenna that can be used to change the amount of energy that is reflected back by the tag. These tags can transmit data to the reader by selectively varying the impedance to modulate the backscattered signals. Similarly, these tags can be put into a “muted” or non-responsive state by selecting and maintaining an impedance value that minimizes the backscattering from that tag.
Thus, an RFID reader can be used to select one or more RFID tags and retrieve data from the selected tags. As such, RFID tags can be used to identify and track large numbers of objects. Furthermore, because RFID tags have a relatively low per-unit cost, they have the ability to track large numbers of objects at relatively low costs.
One issue in large RFID deployments is the potential for interference between RFID readers. Interference can result when multiple RFID readers in an area attempt to transmit to RFID tags at the same time. This interference can prevent reliable reading of tags, thus can prevent the RFID system from accurately tracking objects.
Accordingly, it is desirable to provide an improved system and method for managing RFID readers to reduce interference between readers and improve the reliability and accuracy of the system. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.